Is it dooming? If not, it should be. Does it carry the essence of chaos and corruption? Again, if not, it should.

I think just adding those two should be enough to give it sufficient drawback.

I'm quite sure it does neither. Adding both doom and essence of chaos would be overcompensation imo. I think either one of them would be sufficient. People refrain from using the girdle of the emperors and the shield of raw steel, for example, while both have fantastic stats.

A simple nerf would also be sufficient, I think. With a PV somewhere in the 20-30 range (25?) it would already be more in line with existing items, as it does penalize DV and to-hit. And some other classes receive really good gifts too, so if it remains a really good item that's ok.

It needs to be at least 5 times its current weigh, and maybe have a speed penalty of -10.

I see no problem with the armor being this good. Chaos knights are not a particularly trouble free class to play with and neither does being a crowned champion of chaos make your life particularly easy. It's the best artifact armor in the game, sure, but it's very fitting and thematic, and a moderately high PV does not make you totally invulnerable. There are other very powerful artifacts in the game like Vanquisher or Justifier for a paladin and they do not unduly imbalance the game. The one thing I could agree with would be making it heavier, considering that Perion's is 450s, for example. It could perhaps be twice as heavy considering that a regular iron full plate is 800s.

I agree with grobblewobble. It probably needs some slight nerfing but that CHAOS+Doom would be too much nerf. It would make it just not worth using.

Sorry for the off topic, but does Greater Identify say this causes others to hate you?

for mine this artifact doesn't need too much nerfing (maybe the STR could drop a tad)

Perserver for a wizard is just as good imo.

Maybe the unholy aura effect could apply also when you only carry the artifact in your backpack. Thus it would be harder to walk through eg dwarftown with the artifact. Or make it permacursed, it would have a similar effect. Don't know if its enough to balance but it could be used additionally to other nerfs.

If the armor is modified I think Grey's solution is the most elegant (upped weight plus speed penalty).

Yep, I think it should be toned down a bit, but PLEASE do not make it dooming or contain CHAOS, that would just make it one of those close to useless artifacts again.. Grey's suggestion of higher weight and a speed penalty sounds good. -10 and 1500 pounds weight sounds about right. It would still be a top artifact, but this reduce it's OP:dness by a fair amount, especially in the early game.

IIRC, that armour gives like +10ST which [assuming one does train ST to 15ish by beeing burdened] more than covers 1500 stones caryying capacity. Unless you really mean pounds in which case it is like 6.5k stones

For start I would suggest removing ST bonus and adding like -30 to speed.

I don't think the armor is overpowered, personally. My most recent CK had his base STR exchanged to 3 (6 max potential!) by a potion, and the armor saved his bacon for a long time. The extra strength is +5 to hit and damage, more carrying capacity--not really a big deal. And the enormous PV is great, but it wasn't enough to save me from the Eternal Guardian, or to keep me from getting hurt badly in several combats.

Ben.. of course it didn't save you from the eternal guardian, he ignores PV. The armor could be +1000 PV and it still wouldn't help against the eternal guardian. That doesn't make it any less overpowered.

That would be a change in the bad direction. Most CKs start the game with Str in the twenties, so losing the strength boost isn't such a big deal [esp with GoGS and gauntlets of strength being around]; losing speed while giving the same PV means an incredibly easy early game XP in form of Barnabas and Munxip [strained + this speed down = almost double exp?]

My suggestion would be dropping the PV to +15 or something, give a bigger DV negative and leave it like this - it'd be still a very good crowning gift, making anyone who get it feel happy and not a wasted effort while making it less overpowering in the overall run

If this is Chaos knight only artifact maybe. however I was under impression we are a bit past the age of class/race specific artifacts.

with around what, 17 new Artifacts added, one or two being -slightly- overpowered [like Vanquisher or SAoC&T] isn't such a issue

it'll still be only like, what, 2% chance to get that specific on in precrown/surge/vault, even lower in shop/random drop

@edit

I'm actually wondering if I shouldn't put BoW/Preserver/Nature's Companion instead of Vanq there. They are more universally useful

I think we are going a bit overboard here and mistaking "very powerful" with "overpowered". It is clear to everyone that the armor is very powerful. Some artifacts are significantly more powerful than others. This is clearly a design choice and responds to flavor and lore as much as it does to the artifact's effect on gameplay. Vanquisher is an immensely powerful weapon. So is Justifier in the hands of a paladin. Chaos knights have a 1 in 6 chance to be crowned with this armor. Barbarians have a 2 in 6 chance to be crowned with Vanquisher. The chaos knight design concept is clearly to be powerful hulking warriors donning powerful armor and wielding two handed weapons. All artifact armor gifted to chaos knights offers great PV (helmet gives 12 and boots give 24). No artifact makes you invulnerable. Big chunky armor offers PV at the expense of DV. It makes sense to me. Let's say for the sake of argument that the PV on the armor is slashed down to 30 instead of 40. It would still be very powerful PV. I don't think this is necessary. Adding or enhancing some negatives, while keeping positive and negative attributes thematic, seems to be the best way to go. Throwing an element of lore out of the game in the name of balancing supposed game-breaking properties is not a good idea in my book (and these game-breaking properties are a matter of debate; I don't think any artifact guarantees anything in a game like Adom). Upping the weight, perhaps introducing a speed penalty, and/or making the DV penalty higher, makes sense to me design wise.

(A semi-related comment:

The xp bonus for reduced speed seems to me to be a broken mechanic. I understand the reason for high speed reducing xp gain - it counteracts the effects of staying in the quickling tree and pumping your base speed up to 300 or so - but I think reduced speed augmenting xp gain is a mechanic that only promotes situational cheesing/scumming/abuse. There is no known way of permanently reducing your base speed besides corruption. What is the purpose of the xp gain bonus per reduced speed mechanism anyway? Perhaps this formula should only kick in when speed at the time of killing is 100 or higher.)

In response to the semi-related comment:

Being slower does make fights that more dangerous. The only cheesy bit I see about it is that you can get a monster to critically wounded, then slow yourself and finish off the monster.
(With the slow monster spell or by getting bloated and strained, or wearing boots of the slow shuffle.)

I don't agree that xp gains are an issue with a speed penalty. The need to crawl around at slower speed generally far outweighs xp gains imo, especially on an armor that you cannot quickly put on or take off when it's convenient.

Personally I would like to see Vanquisher being toned down too.

If one would take Justifier as good artifact, why not make these, who I would freely call overpowered, more class based too. Like vanquisher and armor works as now in hands of chaos knight and barbarian but for anyone else it is "toned down"?
For armour I would say half PV and remove St bonus, for chaos knights make St bonus equal to number of corruptions.